Preheat your oven to 375°F and grease a 9x13-inch baking dish with cooking spray or olive oil. Heat olive oil in a large skillet over medium heat, then add the ground beef. Break it apart with a wooden spoon and cook for 5-7 minutes until completely browned with no pink remaining. Drain excess fat if needed.

Add the chopped onion and minced garlic to the skillet with the cooked beef. Stir everything together and cook for 3-4 minutes until the onion turns soft and translucent.

Spread the beef mixture evenly across the bottom of your prepared baking dish. Layer the thinly sliced potatoes on top in an overlapping pattern. Season the potato layer generously with salt, pepper, Italian seasoning, and paprika.

Sprinkle both cheeses over the potatoes, distributing them evenly. Pour the beef broth around the edges of the casserole and drizzle with milk if using. Cover tightly with aluminum foil and bake for 30 minutes.

Remove the foil and bake for an additional 15-20 minutes until the cheese turns golden and bubbly and the potatoes are fork-tender. Let the casserole rest for 5 minutes before serving. Garnish with fresh parsley if desired.